The present invention relates to computer and other networking, particularly devices that can communicate over a network using Transport Control Protocol (TCP) over Internet Protocol (IP). Recent advances in this area include intelligent network interface hardware and software that has been developed by Alacritech, Inc. to work with a host computer. Detailed descriptions of such advances, as well as relevant claims, can be found in U.S. Pat. No. 6,226,680, U.S. Pat. No. 6,226,680, U.S. Pat. No. 6,247,060, U.S. Pat. No. 6,334,153, U.S. Pat. No. 6,389,479, U.S. Pat. No. 6,393,487, U.S. Pat. No. 6,427,171, U.S. Pat. No. 6,427,173, U.S. Pat. No. 6,434,620 and U.S. Pat. No. 6,470,415, which are incorporated by reference herein.
For example, in one embodiment multiple TCP connections can be passed from a host computer to an intelligent network interface card (INIC) that is coupled to the host computer, offloading the TCP processing from the host to the card for these connections. A host can be a computer that acts as a source of information or signals. The term can refer to almost any kind of computer, from a centralized mainframe that is a host to its terminals, to a server that is host to its clients, to a desktop PC that is host to its peripherals. In network architectures, a client station (user's machine) may be considered a host, and an adapter that terminates TCP may also be considered a host, because each is a source of information to the network in contrast to a device such as a router or switch that merely directs traffic at the IP level.
For an INIC to be cost-effective, its processing power and memory capacity may be less than that of the host computer, although the INIC may also be more efficient than the host at certain tasks. TCP protocol guarantees reliable delivery of data, however, requiring thousands of lines of instruction code to ensure that the data is accurately and completely transferred over the network from a source in one host to a destination in another host. For this reason, the host may establish the TCP connections and retain a fallback capability for error handling of messages that are otherwise processed by a fast-path provided by the INIC.
One way that TCP guarantees delivery of data is through the use of acknowledgments (ACKs) and the sequenced delivery of the data. That is, after data has been sent in sequential packets, ACKs are returned from the receiving host indicating that all bytes up to a certain sequence number have been received. As shown in the prior art diagram of FIG. 1, to transmit data corresponding to a TCP connection from a local host having an attached INIC to a remote host over a network, the local host first sends 20 to the INIC a command to transmit the data. The INIC then 22 acquires the data, divides it into segments and adds TCP and IP headers to each data segment to create a TCP/IP packet corresponding to each segment. Next, the INIC transmits 24 the resulting packets onto the network. After the remote host has received and validated the packets, the remote host sends ACKs back to the local host indicating how much of the data has been successfully received.
Upon receiving an ACK 26 for all the transmitted data, the INIC sends a command complete 28 to the local host indicating that the transmit command has been completed by the transport function of the INIC, and an upper layer such as a session layer of the host is informed that its request to transmit data has been completed. For the case in which an ACK is not received by the INIC within a predetermined time after the corresponding packets were sent, indicating an error condition, the TCP connection is flushed 40 from the INIC to the host. The host can then retransmit 44 some or all of the unacknowledged packets.